JP6258393B2 - Condenser - Google Patents

Description

  The present invention relates to a condensing device for use with a particle counter. In particular, the present invention relates to a condensing device that can increase the effective diameter of nanoparticles mixed in a gas, thereby enabling an optical particle counter to detect these particles.

  There is great interest in the health effects of nanoparticles accidentally discharged into the air. For example, the recent 500% increase in respiratory illnesses and allergies in the UK is partly associated with particles emitted by diesel engines and other combustion processes. The main focus is diesel exhaust, but attention is focused on other potential sources such as fossil fuel power generation, incineration, nuclear power generation and aircraft exhaust. All heavy industries, including gas emission processes, have the potential problem of discharging nanoparticles. Such treatments include smelting, firing, glass making, welding, soldering, nuclear power generation and incineration. Other private companies are also concerned that powder detergent enzymes, powder coatings, fibers used in disposable diapers, and other products may cause problems. In addition, the US Environmental Protection Agency is very concerned about gasoline engine emissions.

Nanoparticles are known to produce toxic effects. For example, nanoparticles interfere with the human blood-brain barrier, and gold nanoparticles move from the mother to the fetus through the placenta. Early studies with PTFE (polytetrafluoroethylene) particles about 20 nm in diameter showed that even atmospheric concentrations of inert insoluble material below 50 μg / m ³ were fatal to rats. Furthermore, nanotubes cause more toxic reactions in rats than quartz dust.

  In addition to health concerns, the reduction or control of atmospheric nanoparticles helps maintain many cleanroom standards in the microelectronics, pharmaceutical, medical, laser, and fiber optic industries, etc. is important.

「ナノ粒子」という用語は、１ｎｍ〜０．１μｍ（１００ｎｍ）の範囲における空気力学的な大きさを有する粒子に関して用いられる。 The fine particles are classified as shown in Table 1 below.

The term “nanoparticle” is used in reference to particles having an aerodynamic size in the range of 1 nm to 0.1 μm (100 nm).

  For spherical particles, the aerodynamic particle size is the diameter of the particle. Actual particles in the air have a complicated shape. For non-spherical particles, the term “diameter” is not strictly true. For example, the pieces or fibers have different dimensions in different directions. Even particles of the same shape may be composed of different chemical substances and have different densities. Due to the different shapes and densities, the definition of particle size is quite confused.

Thus, the terms “aerodynamic particle size” or “aerodynamic diameter” are used to provide a single parameter that represents an actually non-spherical particle having any shape and density. As used herein, the term “aerodynamic diameter” refers to 1 g / cm ³ having the same inertial properties (final settling velocity) in air (standard temperature and pressure), like the particles in question. It is the diameter of a spherical particle having a density. The aerodynamic diameter can be set by an inertial extraction instrument such as a cascade impactor. The term “aerodynamic diameter” is convenient for all particles, including masses and aggregates of any shape and density. However, since non-spherical particles usually have a slower final settling velocity than spherical particles, the aerodynamic diameter is not the actual geometric size. Other convenient similar diameters are diffusion diameters or thermodynamic diameters defined as 1 g / cm ³ spheres with the same diffusivity, like the particles in question.

  The investigation and monitoring of nanoparticles in the atmosphere is hampered by the lack of instruments capable of measuring the nanoparticle range that are sufficiently inexpensive and robust and suitable for convenient use in a wide range. It was.

  Several devices are known that measure nanoparticles using laser light to detect and measure particles. However, optical measuring instruments cannot be easily used to detect particles in the size range of nanoparticles, so a technology has been developed that allows the particles to be "grown" and detected. This technology is the basis for the condensed particle counter. Condensed particle counters (CPCs) operate by passing a sample of particles in the air through a chamber containing the evaporated liquid and then through the condenser, where the evaporated liquid is deposited on the particles in the air. To form droplets of measurable size. An example of such a device is disclosed in International Publication No. WO 02/029382 (Ahn et al.). The CPC disclosed in WO 02/029372 comprises a cylindrical evaporation chamber aligned with a porous absorbent support formed of a material such as a nonwoven fabric. At one end of the evaporation chamber, the porous absorbent support is in contact with a reservoir of a volatile liquid, such as isobutanol, so that the liquid moves along the absorbent support and penetrates by capillary action. ing. The outer surface of the evaporation chamber is surrounded by a heating element that heats the evaporation chamber so that isobutanol evaporates from the absorbent support and fills the evaporation chamber with steam. An atmospheric sample containing particles in the air is introduced into the evaporation chamber at the end of the reservoir, through which the isobutanol vapor is condensed onto the particles in the air and can be measured using an optical particle counter. Flowed through a condenser that forms drops.

  An example of a commercially available CPC utilizing the principles disclosed in International Publication No. WO 02/029322 is a model 3025A ultrafine condensate particle counter (Model 3025A Ultrafine) available from TSI, Shoreview, Minnesota, USA. Condensation Particle Counter).

Another known device is a small CPC 3007 from TSI ( www.tsi.com ), the operation of which will be described in detail below with reference to FIG.

  Current condensed particle counters suffer from a number of drawbacks. For example, high power consumption for heating the working fluid and long preparation time (10 to 20 minutes) before use are required. These disadvantages arise at least in part because the evaporation chamber must be heated by an external heating element and the entire case surrounding the evaporation chamber must be heated to bring the instrument to operating temperature. Furthermore, since known CPC consumes a relatively large amount of working fluid (isobutanol), the working fluid must be replenished frequently and sometimes before each use. Even in the case of the TSI US3007 small condensed particle counter, the working fluid cartridge filled with working fluid must be periodically replaced. Yet another disadvantage of the known CPC is that the working fluid used (eg isobutanol) has an unpleasant odor and is relatively expensive.

  Thus, at present, there is a need for a condensed particle counter that can be used for a long time without replenishing the working fluid, shortens the preparation time, and contributes to downsizing.

  The present invention provides a condensing device that, when used in a condensing particle counter, can eliminate or at least reduce all the above-mentioned problems associated with known CPC.

  In a first aspect, the present invention is an apparatus that increases the size of gas entrained particles and allows the gas entrained particles to be detected by a particle detector, comprising an evaporation chamber and a condenser, the evaporation chamber comprising: An inlet for allowing gas to flow into the evaporation chamber; and an outlet for discharging gas containing vapor from the evaporation chamber. The evaporation chamber is provided with a heating element and a porous support, and the heating element is porous. In direct contact with the support, the porous support holds the vaporizable material, and the heating element can be heated to vaporize the vaporizable material and generate vapor in the evaporation chamber And the condenser is in fluid communication with the outlet of the evaporation chamber and has an outlet connected to the particle detector so that the gas containing the vapor from the evaporation chamber can enter the condenser. Flow, gas in the condenser Vaporizable materials condense on incoming particles is large size of the particles, provide a device which is configured to be detected by a single particle detector.

  In one embodiment, the evaporation chamber has at least two inlets, one allowing sample gas containing gas entrained particles to flow into the evaporation chamber and the other being connectable to a carrier gas source that is generally free of particles. It is said.

  In other embodiments, the condenser has at least two inlets, one inlet is in fluid communication with the evaporation chamber, and the other inlet receives a sample gas containing gas entrained particles. Let it flow into the condenser.

  In the second aspect of the present invention, the gas entrained particle size is increased, and the gas entrained particle can be detected by a particle detector, wherein a vaporizable substance source and a vaporizable substance are vaporized. A heating means for forming a vapor, an inlet for introducing a sample gas containing gas-containing particles, and a condenser provided with an outlet connected to the particle detector are provided. Characterized in that the vaporizable substance is selected from dimethyl phthalate, dioctyl phthalate and dimethyl sulfoxide in an apparatus configured to condense in, increase particle size and be detectable by a particle detector Is provided.

  In yet another aspect, the present invention provides a condensing device that increases the size of gas entrained particles and allows the gas entrained particles to be detected by a particle detector, wherein the condensing device is in fluid communication with the evaporation chamber, A condenser having an outlet connected to a particle detector, and a heating element and a porous support provided respectively in the evaporation chamber: the porous support holds a vaporizable substance and the heating element is vaporized A first inlet that can be heated to vaporize possible materials and generate steam in the evaporation chamber, and to flow the vapor stream into the evaporator chamber to flow the vapor to the condenser; and a porous support A second inlet through which a sample gas stream containing gas entrained particles is introduced, and a substance that can be vaporized on the gas entrained particles in the sample gas is condensed in the condenser. The dimensions are increased and the grains A configuration the condenser so as to be detectable by the detector.

  As described above in the introductory part of this application, many particle counters, especially based on optical methods of particle detection, cannot efficiently detect and count particles having a particle size less than about 300 nm. By means of the condensing device of the present invention, particles with smaller dimensions (eg aerodynamic particle sizes smaller than 3 nm) can be detected and vaporized and condensable substances can be condensed on the particles and grown. The above is realized.

  The vaporizable substance is a liquid or a vaporizable solid. When the vaporizable substance is a solid at room temperature, it is preferably a substance that first melts into a liquid and then turns into a vapor, rather than a substance that sublimes from a solid state.

  Examples of solid materials used as vaporizable substances include solid hydrocarbons and long chain carboxylic acids which are fatty acids such as stearic acid.

  However, at present, the vaporizable substance is preferably a liquid.

  Liquids used include water, propanol, isopropanol, and isobutanol, or high-boiling organic liquids. As mentioned above in the introduction, one of the disadvantages of known condensed particle counters is that the liquid used as the vaporizable substance is consumed in a relatively short time, and therefore new liquids are frequently poured. It must be. Some known condensed particle counters require a liquid to be added each time a condensing device is used.

  In order to eliminate the disadvantages of the known condensed particle counter, it is preferable to use a liquid having a boiling point of at least 110 ° C. as a vaporizable substance at room temperature.

  One group of preferred vaporizable liquids consists of dimethyl phthalate, dioctyl phthalate and dimethyl sulfoxide. By using a liquid with a higher boiling point, such as dimethyl phthalate, the consumption rate of the liquid is greatly reduced and it is not necessary to add liquid frequently.

  If the vaporizable substance is a liquid and the evaporation chamber contains or is connected to a liquid reservoir, tilting the condensing device (eg during movement) causes the liquid to escape from the inlet or outlet of the evaporation chamber. There is a possibility of leakage. In order to prevent or minimize the occurrence of this leak, the evaporating chamber inlet and outlet can be provided with lips or rims that act as liquid obstructions. The height of the rim or lip corresponds to the amount of liquid retained in the reservoir. The lip or rim is defined or provided by the end of an inflow or outflow tube that extends into the evaporation chamber. In one example, the height of the rim or lip is 1 mm to 8 mm, preferably 2 mm to 5 mm.

  The carrier gas is air, pure gas, or mixed gas. For example, the carrier gas may be nitrogen gas instead of air. The carrier gas is preferably filtered so that particles and other impurities are not conveyed to the condenser through the evaporation chamber. The carrier gas can be supplied from a gas source that does not contain particles, such as a gas cylinder. Optionally or additionally, a filter can be provided outside the evaporation chamber. For example, by providing a filter at a position that intersects the first inlet itself or upstream of the first inlet, in both cases the carrier gas flowing into the evaporation chamber may contain impurities, in particular Fine particle impurities are not included. Examples of filters include HEPA filters and well known filters that do not require detailed description.

  In other arrangements, the carrier gas is filtered after entering the evaporation chamber. For example, in certain embodiments, the filter consists of or comprises a porous support for the vaporizable material. In this embodiment, the porous support divides the evaporation chamber into upstream and downstream chambers and functions as a filter membrane extending across the interior of the evaporation chamber. The carrier gas flowing into the upstream chamber through the first inlet contains particulate impurities that are removed when the carrier gas passes through the porous support, in which case the vaporizable gas present in the porous support is present. The material is vaporized and steam is sent by the filtered carrier gas. Thus, there are no particulate impurities on the downstream side of the porous support. “Fine particle impurities” refers to particles other than those detected and counted.

  The porous support can have various shapes and can be formed of various materials. For example, the porous support can be formed of a porous material such as a porous ceramic material, glass fiber cloth, quartz fiber filter asbestos or cotton fabric. The porous material must be stable at the temperature used to vaporize the vaporizable substance, and if the vaporizable substance is a liquid, it should preferably be wettable by the substance.

  A temperature sensor (for example, a thermocouple) is usually provided in the evaporation chamber and detects the temperature inside the chamber. The temperature sensor is preferably in contact with or in close proximity to the heating element. The temperature sensor is provided so as to be surrounded by the heating element and / or the porous support. Usually, the temperature sensor is connected to a temperature control device.

  The heating element can take a variety of forms, in which case the heating element is provided within the evaporation chamber and (in the case of known commercially available condensate particle counters) rather than surrounding the outer surface of the chamber. Rather is close to the porous support. The great advantage of providing a heating element in the evaporation chamber is that the preparation time of the apparatus is significantly shortened and the power consumption is considerably reduced. Thus, the CPC including the condenser of the present invention can be warmed to the operating temperature in 1 minute or less compared to the 10-20 minutes required to reach the operating temperature with known CPCs.

  Most preferably, the heating element is in direct contact with the porous support.

  For example, the porous support can be surrounded by a heating element.

  In certain embodiments, the heating element comprises a rod portion (eg, a cylindrical rod) and a porous support surrounding the rod portion (eg, a cylindrical rod). For example, the porous support comprises a sleeve that fits into the rod portion (eg cylindrical rod) of the heating element. Such a configuration is particularly preferably used when the porous support is made of a porous material as described above.

  The porous support (eg, sleeve) has a portion that extends downstream, and in use, extends to a reservoir of a vaporizable substance (in the case of a liquid).

  The rod portion of the heating element has a hollow interior in which a heating wire or heating probe and optional thermocouple are provided. To ensure good thermal contact between the heating wire or heating probe and the inner surface of the hollow rod, use a thermally conductive filler to heat the heating wire or heating probe and thermocouple (if present) ) May be held at a predetermined position. Examples of thermally conductive fillers include solder, other fusible gold, and thermally conductive resins such as metal particle filled resins (eg, epoxy resins).

  A vaporizer incorporating a heating element of the type described above is novel and has yet another aspect of the present invention. That is, in another aspect, the vaporizer is used in a condensed particle counter, and is provided to be attached to an evaporation chamber wall in the condensed particle counter and to extend inside the used evaporation chamber. A heating element comprising a rod part, a porous support that surrounds and contacts the rod part to hold or hold a vaporizable substance, and a choice to hold the porous support in place on the rod part A vaporizing device is provided which comprises a general holding means.

  The rod portion of the heating element and the porous support can be as described above.

  The holding means comprises or consists of a clip or a perforated sleeve adapted to the porous support so as to hold the porous support in place.

  The cross-sectional shape of the evaporation chamber is variable, and can be, for example, a circular or rectangular cross section.

  The apparatus of the present invention can be provided with a second inlet through which a sample gas stream containing gas entrained particles to be counted is introduced. The second inlet is provided to open to the evaporation chamber, an intermediate chamber between the evaporation chamber and the condenser, or the condenser.

  In one embodiment, a second inlet is provided to open into the evaporation chamber. The second inlet may have a nozzle that extends into the evaporation chamber. When the second inlet is located in the evaporation chamber, the second inlet is aligned with an outlet opening in communication with the condenser, for example, such that the longitudinal axis of the inlet is aligned with the longitudinal axis of the condenser. Is preferred. For example, in the case of a circle, the second inlet has a cross-sectional area that is smaller than the cross-sectional area of the outlet opening, such that the second inlet has a diameter that is smaller than the diameter of the outlet opening (if circular). It is preferable. In this example, without relying on any theory, the sample gas flow or jet is surrounded by a concentric layer of carrier gas and vapor as it exits the evaporation chamber, and the two concentric layers move through the condenser. When you mix.

  In another embodiment, a second inlet is provided to open to the condenser. Preferably, the outlet opening of the evaporation chamber is provided with a nozzle that extends to the condenser and is located alongside the second inlet or downstream of the second inlet. In this arrangement, without relying on any theory, the carrier gas stream and vapor from the evaporation chamber are surrounded by a concentric layer of sample gas as it enters the condenser, and the two concentric layers move through the condenser. When you mix.

  If the second inlet is open to the condenser, some or all of the sample gas is saturated with the vapor before entering the condenser. In this embodiment, the second inlet is connected to an auxiliary evaporation chamber.

  In yet another embodiment, the second inlet is provided to open into an intermediate chamber between the vapor chamber and the condenser, the intermediate chamber being divided into upstream and downstream subchambers by a dividing wall, The central hole in the wall communicates with the subchamber so that the second inlet is open to the upstream subchamber and the third inlet is open to the downstream subchamber. Is connectable to a filtered gas supply and extends from the outlet opening of the evaporation chamber into the condenser, alongside the second inlet, at the position of the upstream subchamber, or the second stream. A nozzle is provided at a location downstream of the inlet, and the downstream subchamber includes a cylindrical baffle aligned with the nozzle and a central hole in the dividing wall, and a third nozzle opens into a space surrounding the cylindrical baffle. ing.

  In the above arrangement, without relying on any theory, the carrier gas stream and vapor from the evaporation chamber are surrounded by a concentric layer of sample gas as it flows from the nozzle into the upstream intermediate subchamber. When two concentric layers of carrier gas / vapor and sample gas flow into the downstream intermediate chamber through the central hole in the dividing wall, other concentric layers of filtered carrier gas that flowed in through the third inlet Surrounded by. In this way, a three-layer flow of gas consisting of the core flow of the carrier gas and vapor, the intermediate layer of the sample gas containing the gas-containing particles, and the outer layer of the filtered carrier gas is temporarily formed. The three-layer flow of gas then flows out of the intermediate chamber through the interior of the cylindrical baffle to the condenser where these three layers are mixed.

  In each of the above-described embodiments, when the heated carrier gas, sample gas, gas entrained particles, and vapor mixture pass through the condenser, the gas is cooled in the condenser, and vapor and supersaturation of vaporizable material. And condenses on the surface of the particles. If the vaporizable substance is a liquid, drops are formed on or around the particles, while if the vaporizable substance is a normal solid at room temperature, it is cooled to contain or hold the particles It becomes. In this way, the particles are efficiently enlarged to a size exceeding 3 nm to 1 μm. By making the particles larger, they can be detected by an optical particle detector such as an optical particle counter.

  Typically, the condenser is formed long enough with a material with high thermal conductivity, the mixture of carrier gas, sample gas, vapor and particles to be detected is sufficiently cooled, vaporizable material condenses on the particles, Grows to a detectable size (for example, 1 μm or more). Thus, the condenser is formed into a tubular shape with a metallic material such as aluminum or stainless steel. The wall thickness of the condenser and other components of the device is as thin as possible, but when using the device at high pressure or reduced pressure (eg 10 bar), the wall thickness should be sufficiently thick to withstand such pressure. There is a need to.

  Cooling means may be provided to assist in cooling the gas, vapor and particle mixture in the condenser.

  In one embodiment, the cooling means comprises one or more fans that each send an air flow to the outer surface of the condenser. In one embodiment, there is one fan. In other embodiments, there are two fans.

  Optionally, the fan may be part of the air temperature control device. The temperature controller allows the air that cools the condenser surface to be maintained at a specified temperature that is not affected by the temperature of the air surrounding the condensation chamber.

  Alternatively, the cooling element may be provided in contact with the outer surface of the condenser. The cooling element is, for example, a thermoelectric cooling device (for example, a Peltier cooling device).

  In order to further cool, the cross section of the condenser may be formed so that the ratio of the circumference to the cross-sectional area is increased.

  The condenser preferably has a ratio of surface area to volume that is greater than a ratio of surface area to volume of the cylindrical portion. By increasing the surface area to volume ratio, the condenser can be cooled more efficiently and rapidly, thereby reducing the size of the condenser.

  The condenser has a length (dimension corresponding to the distance between the inlet and outlet of the condenser), width (dimension perpendicular to the length) and height (dimension perpendicular to the length and height) Is defined as In the case of a circular cross-section tubular condenser, the width and height are the same and correspond to the diameter of the tube. In the case of a rectangular condenser with a square cross section, the width and height are the same. However, in this application, the width and height of the condensers are not the same, and the term “height” means the shorter of the two dimensions.

  The ratio of surface area to condenser volume can be increased in various ways. For example, at least a part of the condenser may have a partially flat cross section, or an elongated oval or rectangular cross section, that is, a cross section in which the height of the condenser is generally shorter than the width. In one embodiment, the condenser has a generally rectangular cross section and a height that is less than half the width.

  In other embodiments, the condenser comprises a condenser body that is annular or partially annular. The annular body of the condenser contains heat vapor containing gas flowing through the annular gap between the inner cylinder and the outer cylinder, and cooling air flowing around the outer surface of the outer cylinder or together with the outer surface of the inner cylinder. Formed with two concentric cylinders containing.

  It is important to ensure that the residence time of each particle in the condenser is approximately the same so that the particle size can be accurately measured. This means that the flow rate and flow path of the particles flowing through the condenser should ideally be as uniform as possible.

  When a non-cylindrical condenser (eg, a rectangular condenser) is connected to a line of cylindrical inlets and outlets, the width of the condenser (as defined herein) is particularly limited. If it is larger than the diameter of the outlet, there may be a non-uniform flow between the inlet and outlet. To eliminate this potential problem, a condenser (eg, a generally rectangular condenser) can be provided with a pair of flow distribution lines that are aligned generally perpendicular to the length (flow direction) of the condenser. it can. The flow distribution pipes are connected to the inlet and outlet of the condenser, each forming a row of elongated slots or holes that extend across the width of the condenser and open into the interior of the condenser.

  According to another aspect of the present invention, there is provided a condenser used in the above-described apparatus of the present invention, the condenser having an inlet, an outlet, and a hollow interior having an inner length, an inner width and an inner height. Connected to the inlet of the condenser body and the inlet of the condenser body, and connected to the inlet of the condenser body and the inlet pipe for the inflow flow extending across the inner width of the condenser body. And the inner height of the condenser body portion is lower than the corresponding inner height of each of the inflow distribution pipe and the outflow distribution pipe, Each wall of the inflow distribution pipe and the outflow distribution pipe is provided with one or more slots or holes that communicate with the hollow interior of the condenser body, and from the inflow distribution pipe through the hollow interior of the condenser. A flow path leading to the outflow pipe is formed Condenser is provided.

  In use, is the outlet of the evaporation chamber attached to the inlet flow distribution pipe, or is the fluid outlet connected to the outlet of the evaporation chamber, while the particle detector is attached to the outlet flow distribution pipe? Or an outflow detector is fluidly coupled.

  A flow distribution pipe is provided and the slot or hole is positioned so that the gas flow flows generally uniformly through the condenser body to the particle detector.

  The flow distribution pipe may be, for example, a circular cross section, an oval cross section, or a polygonal cross section (regular polygon or non-regular polygon). In one embodiment, the flow distribution pipe has a circular cross section.

The inner cross-sectional area of each flow distribution pipe is preferably larger than the inner cross-sectional area (inner width × inner height) of the condenser body. As an example, if the cross section of the flow distributor is circular with an inner diameter Dt, the inner height of the condenser is Hc, and the inner width is Wc, then πDt ² > Hc ^* Wc. The ratio of πDt ² / (Hc ^* Wc) is usually greater than 1.1, preferably greater than 2 and more preferably greater than 3.

  As noted above, the fluid connection between the interior of the flow distributors 102 and 104 and the interior of the rectangular condenser is an elongated slot that opens into the hollow interior of the condenser body at the wall of the flow distribution line. Or by forming a (preferably linear) array of holes. The flow distribution pipes and the interior of the condenser body are fluidly connected by a narrow slot in the wall of each flow distribution pipe. Since the uniformity of the flow in the condenser is based on the ratio of the inner height (Hc) of the condenser to the slot width (Ws), the inner diameter of the flow distribution pipe can be reduced by making the slot thinner. In this context, slot width is the dimension in the same direction as the inner height of the condenser (in contrast, the “length” of the slot referred to as “length” is the same as the inner width of the condenser. Direction dimension). Usually, the ratio Hc / Wc is greater than 1.1, preferably greater than 2 and more preferably greater than 3.

In other embodiments, the flow distribution wall includes holes formed uniformly along the inlet and outlet of the rectangular condenser 103, instead of slots. The number of holes Nh is greater than 1, preferably greater than 4 and more preferably greater than 10. The diameter of the hole Dh should be sufficiently small and is represented by the formula πDt ² > Nh ^* πDh ² . The ratio of πDt ² > Nh ^* πDh ² is greater than 1.1, preferably greater than 2 and more preferably greater than 3.

  The flow distribution line can be formed of a variety of materials, such as stainless steel rigid tube, PTFE, aluminum, or other suitable metal, glass, ceramic or plastic material. The condenser body is preferably formed of a thermally conductive material such as stainless steel, for example, metal steel.

  One potential problem, particularly when the condenser has a small internal cross-sectional area or width (eg, less than 2 mm), is that the condensate on the condenser wall can be an obstacle. In order to solve this problem, a means for removing condensed substances from the inner wall of the condenser may be provided. For example, a condenser has one or more exhaust ducts that extend over its entire length or part, the exhaust duct being separated from the interior of the condenser by a semi-permeable wall or membrane through which liquid condensate can pass. And has one or more outlets connectable to a pump for extracting liquid condensate from the discharge duct. Semi-permeable membranes are periodically filled with working fluid so that no gas flow can pass through the membrane. With this arrangement, when vaporizable material condenses on the inner wall of the condenser, it is extracted into the discharge duct through the semi-permeable wall instead of accumulating and obstructing the condenser. Removed. Once extracted, the condensate is either sent to a waste storage room for later disposal or recycled to the evaporation chamber.

  A discharge duct can be formed by dividing the interior of the condenser over at least a portion of the length of the condenser by one or more longitudinally extending semi-permeable walls or membranes. A semi-permeable wall or membrane is provided with a capillary that allows condensate to flow from the interior of the condenser to the exhaust duct. For example, the wall or membrane can be formed of a ceramic or stainless rigid filter material having a capillary diameter of less than 0.5 mm, for example 1-10 μm.

  The condensing device of the present invention is usually designed to be connected to a particle detector capable of detecting one particle and / or counting one particle.

  Furthermore, the condensing device of the present invention is designed to be part of a condensing particle counter, so that it is a particle counter, for example, “SAC1” particles available from Nanum Limited, Canterbury, UK. It can be connected to a counter.

  Accordingly, in another aspect, the present invention provides a condensed particle counter comprising the condensing device of the present invention described above.

  In another aspect, the present invention provides a method for detecting and counting nanoparticles using a condensed particle counter comprising the condensing device of the present invention described above.

  Still other aspects and features of the present invention will become apparent from the following specific examples illustrated in FIGS.

FIG. 1 is a schematic sectional side view of a known condensing device. FIG. 2 is a schematic diagram of a condensing device according to a first embodiment of the present invention. FIG. 3 is a schematic diagram of a condensing device according to a second embodiment of the present invention. FIG. 4 is a schematic diagram of a condensing device according to a third embodiment of the present invention. FIG. 5 is a schematic diagram of a condensing device according to a fourth embodiment of the present invention. FIG. 6 is a rectangular cross-section of a condenser in a modified example also serving as an outlet, provided with a working fluid removing means that replaces the condenser also serving as the outlet shown in any one of FIGS. It is a schematic sectional side view of a shape. FIG. 7 is a schematic cross-sectional side view of a condenser provided with a working fluid removal means that replaces the condenser that also serves as the outlet in any one of the embodiments of FIGS. FIG. 8 is a schematic diagram of a condensing device according to a fifth embodiment of the present invention. FIG. 9 shows the aerosol particle number density (N) measured in the condensation chamber of FIG. 2 fitted with a MetOne® laser optical particle counter (black squares) and a small 3007 CPC (white diamond) from TSI. It is a graph to compare. FIG. 10 is a schematic diagram of a condensing device according to a sixth embodiment of the present invention. FIG. 11 is a schematic diagram of a condensing device according to a seventh embodiment of the present invention. FIG. 12 is a schematic diagram of a condenser and particle counting assembly according to an eighth embodiment of the present invention, which allows the working fluid to be reused. FIG. 13 is a schematic diagram of a rectangular condenser with flow distributors at the inlet and outlet of the condenser. FIG. 14 is a cross-sectional (vertical plane) view of a rectangular condenser having flow distributors at the inlet and outlet of the condenser. FIG. 15 is a cross-sectional (horizontal plane) view of a rectangular condenser having a flow distributor at the inlet and outlet of the condenser. FIG. 16 is a cross-sectional (vertical) view of a rectangular condenser having a flow distributor with a slot at the inlet of the condenser and another flow distributor with a slot at the outlet of the condenser. FIG. 17 is a cross-sectional view of an evaporation chamber according to another embodiment of the present invention. FIG. 18 is a schematic cross-sectional view of the evaporation chamber of FIG. 17 viewed from a different angle with the heating element omitted and the working fluid reservoir provided. FIG. 19 is a schematic cross-sectional view showing a plane of the evaporation chamber shown in FIG. FIG. 20 is a detailed cross-sectional view of the heating element and porous support used in the embodiments of FIGS.

  The details of the invention will be described with reference to specific examples described in non-limiting examples.

  FIG. 1 is a schematic cross-sectional side view of a known condenser used in combination with a particle counter. One such known condensing device is that found in the small CPC 3007 from TSI (www.tsi.com). The condensing device comprises an evaporation chamber 1a having a porous support in the form of a cartridge 2a immersed in a volatile working fluid. The evaporation chamber 1a has a cylindrical shape and has an inner diameter larger than the outer shape of the cartridge 2a. The evaporation chamber 1a is provided with an inlet 4a, an outlet 5a, and a heating element 3a that surrounds the outer wall of the evaporation chamber 1a. The temperature of the evaporation chamber 1a is measured by a sensor 6a and controlled by a control unit 7a via an interface 8a connected to a heating element 3a on the outer wall of the evaporation chamber 1a. The condenser 9a is provided between the evaporation chamber 1a and the outlet 5a.

  An air flow containing small gas entrained particles (for example, particles in the air) is drawn into the evaporation chamber 1a through the inlet 4a by a pump (not shown). As it passes through the evaporation chamber 1a, the air stream is heated and saturated with the vapor formed by the evaporation of the working fluid. The steam-saturated air stream then flows to the condenser 9a where the air is cooled and the working fluid condenses on the particles in the air. As a result, the particles grow by condensation to a size of about 1 μm that is easily detectable. The enlarged particles are discharged from the outlet 5a and sent to an optical particle counter that counts the particles.

  The condensing device shown in FIG. 1 can be used to detect and count particles with a size in the range of 10 nm to 600 nm. However, this condensing device suffers from a number of drawbacks.

  One major drawback is that the working fluid must be changed regularly or frequently.

  Yet another disadvantage is that it takes a considerable amount of time to prepare for an operational state. In the case of the above-mentioned TSI CPC3007, the condenser requires a preparation time of 600 seconds before it can be used.

  Another drawback is that the condenser layout does not easily contribute to miniaturization. Miniaturization of the condensing device requires the use of a small working fluid cartridge, which in turn necessitates more frequent filling. Thus, when the size is reduced, the period during which the condensing device can be used without being filled is shortened.

  Yet another disadvantage is that the TSI CPC 3007 described above cannot be used in an elevated pressure environment and will only operate if it is kept level according to product specifications.

  When the working fluid in the CPC cartridge 2a shown in FIG. 1 decreases relatively rapidly, the vapor of the working fluid present in the air in the evaporation chamber 1a becomes low in concentration, which affects the performance of the condenser 9a. . As the vapor concentration is reduced, the vapor is preferably condensed on relatively large particles so that small particles are not detected and counted. For example, the lower detection limit increases from 10 nm to 15 nm or 20 nm because the working fluid decreases. In fact, it is very difficult to actually monitor the degree or rate of reduction, so many small particles may not be detected and counted.

  The condensing device of the present invention solves or at least reduces the problems identified by the known CPC.

A condensing device according to a first embodiment of the invention is shown in FIG. The condensing device
An evaporation chamber 2 having one inlet 1 (“first inlet”) for a clean gaseous medium from which all relevant aerosol particles have been removed, eg clean air;
The flow of the sample gas (eg air) containing the nanoparticles in question is drawn into the evaporation chamber 2 and away from the first inlet 1, for example when the first inlet 1 is located below the evaporation chamber 2 Another inlet 8 located at the top of 2 ("second inlet");
A heating element 3 covered by a porous support 6 that is in sufficient thermal contact with the temperature sensor 4 and is wettable by the working fluid;
The porous support 6 is soaked in a low equilibrium vapor pressure working fluid, for example a semi-volatile organic compound such as dimethyl phthalate, porous to a level that keeps the working fluid at a sufficiently high vapor density; A temperature control device 5 for maintaining the surface temperature of the support 6;
-Constructed of high thermal conductivity material, working fluid drops formed on the nanoparticles in question, with outlets long enough to grow them to a size that can be detected and counted by a single particle counter Condenser 7 which also served as
The condenser 7 is located close to or opposite to the second inlet 8, and efficiently mixes the carrier gas flow and the sample gas flow flowing into the evaporation chamber 2 through the first and second inlets. And aligned with the second inlet 8,
A temperature cooling device 10 provided at a position where the condenser 7 can be effectively cooled, and maintaining the surface temperature of the condenser 7 at a level that maintains the formation and growth of working fluid droplets;
It has. The temperature cooling device 10 is disposed at a position where effective cooling of the condenser 7 can be maintained.

  In use, a clean carrier gas (e.g., air) stream that is filtered through a filter (not shown) and contains no (or little) detectable (amount) of aerosol particles is passed from the first inlet 1 to the evaporation chamber 2. Inflow. In the evaporation chamber 2, the heating element 3 is located in good thermal contact with the temperature sensor 4, and the temperature control device 5 connected to the temperature sensor 4 sufficiently evaporates the working fluid and causes the particles in question. The temperature is controlled to a predetermined temperature that generates a situation necessary for continuing to condense the working fluid. The working fluid is contained in a porous support 6 in the form of a cover 6 provided on the heating element 3. In the case of a cylindrical heating element, the cover is covered by the surface of the heating element and immersed in the working fluid. As a result, the clean air flow introduced through the first inlet 1 is saturated with the working fluid vapor and moves toward the condenser 7. A sample of gas (eg air) containing the nanoparticles in question is introduced into the evaporation chamber 2 via the second inlet 8. In the region between the second inlet 8 and the opening to the condenser 7, the saturated thermal vapor and the unheated stream of sample gas containing the nanoparticles in question are mixed so that the working fluid vapor is supersaturated. Become. Thus, in this region, heterogeneous nucleation of the working fluid begins to occur on the particles in question. When the mixture of the vapor and the sample gas containing nanoparticles flows into the condenser 7, the gas and the vapor are cooled by the wall of the condenser 7. Excess heat is removed from the surface of the condenser 7 by the temperature cooling device 10. FIG. 2 shows a cold air flow 9 generated by the blower. In the condenser 7, drops of working fluid grow on the nanoparticles to a detectable size, for example 1 μm. These drops can be counted using, for example, an optical particle counter (not shown) connected to the outlet 11 of the condenser. Thus, each nanoparticle in question is detected individually.

As in the example of the condensing device shown in FIG. 2, the small and cylindrical evaporation chamber 2 having an inner diameter of 10 mm is made of PTFE, and inlets 1 and 8 formed of a stainless copper pipe having an outer diameter of 4 mm; And a condenser 7 also serving as an outlet formed of a stainless steel rigid tube having an outer diameter of 8 mm. A K-type thermocouple was used as the temperature sensor 4. The heating element 3 used was a NiCr heater covered with a porous SiO ₂ layer immersed in dimethyl phthalate. Particles were counted using a MetOne laser particle counter position (Hach ULTRA Analytics).

  The temperature was controlled by a temperature controller 5 of Digitron. It was found that the condensing apparatus configured as described above can expand the diameter of the nanoparticles to 1 μm to 2 μm. The condenser was used for at least 2 months without refilling.

  Another embodiment of the present invention is shown in FIG. The condensing device of FIG. 3 is similar to the condensing device of FIG. 2 except that a working fluid reservoir 12 is provided to extend the operational time of the device without refilling. In order to prevent fluid from leaking out of the reservoir 12 and disturbing the condensation process when the condensing device is not in a horizontal position, the inlets 1 and 8 and the condenser 7 serving also as an outlet protrude inside the evaporation chamber 2. Is provided. This protrusion prevents the working fluid from leaking from the inlets 1 and 8 and the condenser 7. A condenser of the type shown in FIG. 3 has been found to operate for at least 12 months without refilling.

  The operation mode of this embodiment is the same as that of the embodiment of FIG. 2 described above.

  Yet another embodiment is shown in FIG. In this embodiment, which is similar to the configuration of the condenser of FIG. 2, a cooling element 13 is provided which is in thermal contact with the condenser 7 which also serves as an outlet. For example, the cooling element 13, which can be constituted by a thermoelectric cooling element, is attached to the surface of the condenser 7. The cooling element 13 allows heat to be removed from the condenser 7 more efficiently than using a fan. As the cooling effect by the cooling element 13 increases, the supersaturation of the vapor in the condenser 7 increases, and the droplets of the working fluid can grow rapidly. The operation of the cooling element 13 can be controlled such that the surface temperature of the condenser 7 is lower than the ambient temperature, thereby enabling the condensing device to be used efficiently over a range of ambient temperatures including high temperature environments. The operation of this embodiment is not affected by changes in ambient temperature.

  The shape of the condenser 7 affects the operation. In the embodiment shown in FIG. 5, the condenser 7 has a rectangular cross section indicated by the element labeled 14. In this embodiment, the rectangular cross section 14 is an intermediate region of the condenser 7. On both sides of the intermediate region, the condenser 7 can be any cross section, for example circular. By making the rectangular cross-sectional shape, the area where the cold airflow 9 from the temperature cooling device 10 hits is widened, thereby increasing the cooling efficiency for the condenser 7, promoting supersaturation of vapor in the condenser 7, and droplet growth. Efficiency is improved. Although the condenser 7 is shown as having an intermediate region of a rectangular cross section with a flat side surface, the short side of the rectangle may be rounded instead of flattened to have an elongated oval cross section instead of a rectangle. By simply suitably flattening the part of the tube in which the condenser 7 is formed, an elongated oval cross section can be formed.

  The second inlet 8 may have a rectangular or elongated oval cross section. In fact, the ratio of the height and width of the rectangle is 1-100.

  In each of the embodiments shown in FIGS. 2 to 5, the second inlet 8 is positioned in alignment with the condenser 7, and the inner cross-sectional area of the second inlet 8 is larger than the inner cross-sectional area of the condenser 7. It is getting smaller.

  Without being bound by any theory, this arrangement allows a sample gas (eg, air) stream containing aerosol particles to flow into the center of the vapor stream and the carrier gas so that the mixture flowing into the condenser 7 is transported into the carrier gas. And a central flow of sample gas containing nanoparticles surrounded by a vapor layer. Mixing between concentric layers occurs when gas and vapor move through the condenser 7.

  The cross-sectional shape of the main body portion of the evaporation chamber 2 can also be rectangular like the cross-sectional shape of the heating element 3. The heating element 3 is normally located and oriented so as to optimize the efficiency with which the carrier gas stream entering the first inlet 1 is saturated with the working fluid vapor.

  When the width of the rectangular cross section of the condenser 7 shown in FIG. 5 is small (for example, less than 2 mm), the condensed working fluid accumulates on the inner surface of the condenser 7, thereby causing a risk of clogging the condenser 7. In order to prevent the occurrence, means for removing the condensed working fluid from the condenser 7 can be provided. One way to do so is to combine capillary action and differential pressure to remove the condensed liquid from the inner surface of the condenser 7. An arrangement for realizing this is shown in FIG.

  FIG. 6 is a cross-sectional view of the condenser 7. Inside the condenser are two strong porous membranes 15 that can be wetted by the working fluid and act to divide the condenser into a central channel and a pair of elongated fluid collection chambers 16. Yes. In use, when the vapor flow and the gas containing the nanoparticles flow and the grown droplets flow along the central path between the porous membranes 15, the vapor of the working fluid is condensed on the surface of the porous membrane 15. The excess liquid thus formed is immediately absorbed through the porous membrane 15 and flows into the fluid collection chamber 16 by a combination of capillary action and negative pressure maintained by a pump (not shown). Fluid is removed from the fluid collection chamber 16 via an outlet 17 and flows to a waste collection chamber (not shown) or, in the case of a condensing device having a working fluid reservoir 12 as shown in FIG. 12 is recycled.

  In order to stabilize the temperature of the condenser, it is preferred to control the temperature of the liquid in the fluid collection chamber 16. This can be done by using an external cooling element (eg, a thermoelectric cooling element) as shown in FIG. 4 or by circulating the liquid through a heat exchanger as shown in FIG.

  FIG. 7 is a partial schematic cross-sectional view of a condenser (the remainder of the condenser is not shown) having a fluid collection chamber 16 connected to a working fluid circulation and temperature control device.

  Each fluid collection chamber 16 has an additional outlet 18 that is connected by a long tube. The inflow port 17 and the outflow port 18 are connected to the pump 19 and the temperature control device 20 by long pipes. Further, the inflow port 17 and the outflow port 18, the long pipe as a connecting pipe, the pump 19, and the temperature control device 20 constitute a circuit, and the working fluid is circulated. The working fluid flowing through the circuit via the fluid collection chamber 16 is maintained at a constant predetermined temperature by the temperature controller 20, and in this way, the inner surface temperature of the condenser is controlled.

  In the circuit, an additional pump (not shown) or other liquid feed means causes a portion of the working fluid to flow through the tube 21 to the working fluid reservoir 12 in the main body of the evaporation chamber 2. It has a valve (not shown) that can.

  The tube connections shown in FIG. 7 are merely exemplary and can be arranged so that the liquid can be cooled more uniformly by the condenser. For example, in one arrangement, working fluid flows from temperature controller 20 to inlet 17 and out of outlet 18 to pump 19.

  Also, the left and right fluid collection chambers 16 are maintained at different temperatures. Thereby, the vapor | steam of the working fluid in a condenser becomes further supersaturated, and it can increase / decrease the growth rate and magnitude | size of a droplet as needed. In this case, each fluid collection chamber has its own temperature control cycle. The liquid temperature in the fluid collection chamber can be found experimentally or by nucleation theory through trial and error.

  Maintaining the two fluid collection chambers 16 at different temperatures provides other important advantages. When the supersaturation in the condenser becomes large enough, different sized nanoparticles can form drops at different locations as they move through the condenser, and thus drops formed on different sized nanoparticles. Grow to various sizes. For example, 50 nm particles produce 0.5 μm drops, while 100 nm particles produce 1 μm drops. This allows the size of the nanoparticles to be derived from the size of the droplets and easily forms the basis for a method for characterizing the aerosol size distribution.

  Further, the inner surface temperature of the condenser is non-uniform, and decreases linearly in proportion to the length of the condenser, for example. This gradually increases the supersaturation of the working fluid vapor based on the length of the condenser, thus enhancing the performance of the condensing device to grow different sized nanoparticles to different sized drops. Large nanoparticles tend to form drops early (in front of the condenser), while small particles that require greater supersaturation tend to form drops later in the condenser, resulting in: Smaller particles have a shorter growth time and therefore grow into smaller sized drops compared to larger nanoparticles. This can establish a correlation between the size of the droplets formed in the condenser and the size of the nanoparticles. This relationship can be used to evaluate the size of the nanoparticles by analyzing the size of the drops.

  Supersaturation in the condensing device of the present invention is controlled by wall temperature, condensing device dimensions, carrier gas flow rate, and sample gas flow through the condensing device. By changing these parameters, one skilled in the art can select the supersaturated state. There is a known relationship between supersaturation and the smallest nanoparticle size that can form droplets. Thus, by changing one or several of these parameters, for example the temperature of the heating element 3, the lower detection limit of the condensing device can be changed. This is very useful in determining the size distribution of the nanoparticles and the percentage of nanoparticles in various sizes. Moreover, it can be set as the condensation apparatus of a predetermined | prescribed lower limit of detection, for example, 100 nm, 30 nm, 10 nm, 3 nm, or a variable detection lower limit. This is the basis for the size of the aerosol particles to obtain the size distribution of the nanoparticles.

  Moreover, the several condensing apparatus of this invention set so that it might be set as a different supersaturation state can mutually be connected in series or in parallel. The tandem arrangement allows different sized nanoparticles to grow into different sized drops. If the first condenser is set to a lower supersaturation than the second condenser, large particles will form drops in the first condenser while small particles will only drop in the second condenser. While previously formed drops grow further and become very large. This is also true for the second and third condensers. Thus, a plurality of sizes of droplets can be formed by a plurality of condensers. Thereby, for example, the size distribution of the nanoparticles can be read by analyzing the size distribution of the droplets using an optical particle counter.

  When the condensers are arranged in parallel, the nanoparticle flow in question is divided into several parallel flows, which flow to different condensers. The condenser should be set to different supersaturation values so as to have different magnitude detection limits. Thereby, the number particle size distribution of the nanoparticles can be read by analyzing the number of drops grown in those condensers.

  In addition, the temperature of the condenser and other parameters can be changed, and thus the supersaturation can be changed with a lower detection limit during a given measurement cycle. Thereby, the cumulative size distribution of the particles can be obtained.

  A condensing device according to another embodiment of the present invention is exemplarily shown in FIG. In this embodiment, the condensing device comprises an evaporation chamber (saturation chamber) 2 containing a heating element 3 fed by a controlled power source 5. The heating element 3 is attached to a temperature sensor 4 connected to a controlled power source 5 and is in intimate contact with a porous support 6 immersed in a working fluid, for example a semi-volatile compound. The evaporation chamber 2 has an inlet 1 and an outlet that opens into the condenser 7 and extends into a nozzle 22. The condenser 7 is provided with an inlet 8 through which a gas sample containing the nanoparticles in question is introduced into the condenser 7. The nozzle 22 extends to the condenser 7 and opens to the condenser 7 on the downstream side of the inlet 8. The condenser 7 is provided with an outlet 11 and a cooling member 13.

  The embodiment of FIG. 8 operates as follows. A flow of clean air (carrier gas) is sent to the evaporation chamber 2 via the inlet 1 by a flow generator, for example a pump (not shown). In the evaporation chamber 2, the heating element 3 heats the porous support 6 immersed in the working fluid, and steam is generated. The air stream containing the vapor is sent to the condenser 7 via the nozzle 22, and the air stream is mixed with an unheated sample gas stream containing nanoparticles flowing in via the inlet 8 and cooled. Nozzle 22 is designed to flow an air stream saturated with thermal vapor into the center of a sample gas stream containing nanoparticles, so that the stream saturated with thermal vapor is surrounded by a cold sample gas layer. The The combined gas stream is cooled by a cooling element 13 that controls the temperature of the wall of the condenser 7. In the condenser 7, the working fluid becomes supersaturated as a result of mixing of the air saturated with the hot vapor and the cold sample gas and cooling by the wall of the condenser 7. Thereby, the vapor | steam of a working fluid will condense on the nanoparticle in air, and a droplet of about 1 micrometer will be formed. These drops are sent to the optical particle counter via the outlet 11 and counted individually.

  In order to reduce the disappearance of the particles, the nozzle 22 and the condenser 7 are cylindrically symmetric, the nozzle 22 is located along the axis of the condenser 7 and the nozzle end leads to the second inlet 8. Beyond and extending downstream. This allows a cold sample gas stream to be formed around the carrier gas stream containing the vapor.

  An advantage of the condensing device of the present invention is that it provides reliable data and can be much smaller than known condensing counters.

  The preferred working fluid in each embodiment of the present invention is semi-volatile dimethyl phthalate. The main advantage of using semi-volatile compounds is that the consumption of working fluid is very low. It has been found that the condensing device of the present invention operates with no filling required for more than 10 months.

  The choice of flow rate, evaporation chamber temperature, and method of introducing the particles of interest in the air into the condenser are usually set by the nature and concentration of the particles. The total flow from the outlet 11 of the condenser 7 is often 0.1-4 liters / minute. The clean carrier gas stream is 10% to 90% of all streams. The temperature of the evaporation chamber is usually between 80 ° C. and 150 ° C. for dimethyl phthalate.

  In order to reduce the power consumption of the heating element, a thin film heater with a porous medium wettable by the working fluid can be used. It is preferable that a part of the porous medium is made sufficiently long and in contact with the working fluid at the bottom of the evaporation chamber 2.

  The evaporation chamber 2 and the condenser 7 can be constructed of a variety of materials including any metal, glass, or ceramic, or plastic (such as PTFE in the case of the evaporation chamber), but air or other carrier gas It is preferable to use or surface-treat a material that is inert or resistant to oxidation and does not chemically react with the working fluid. Pyrex glass, quartz, ceramic, and stainless steel were used for various modifications of the chamber and their elements.

  Alternatively, a sample gas flow containing the particles in question may be introduced via the inlet 1 and clean air may be introduced via the inlet 8. This is preferred for particles with a constant temperature, such as metal particles. However, aerosol particles formed of organic compounds are affected by the high temperature generated by the heating element and should therefore be introduced via the inlet 8.

  A condensing device according to another embodiment of the present invention is shown in FIG. In this embodiment, the evaporation chamber 2 has the same design as the embodiment of FIG. 8, and the mixing chamber (intermediate chamber) 25 is provided between the evaporation chamber 2 which is a saturation chamber and the condenser 7. ing. The mixing chamber 25 is divided by a partition 24 having a central hole to the downstream and upstream subchambers. The nozzle 22 extends to the upstream subchamber and a cylindrical baffle aligned with the nozzle 22 extends upstream from the end of the downstream subchamber. These elements can be composed of the same material as the other parts of the condenser. The mixing chamber 25 and the partition 24 are cylindrically symmetric or have a rectangular cross section. With this embodiment, the smallest detection particle size of 1 nm nanoparticles can be realized. A third inlet 23 is provided and opens into an annular space surrounding the cylindrical baffle.

  In this embodiment, the aerosol sample in question flows from the inlet 8 and the clean air stream is introduced from the inlet 23. The mixing chamber allows the aerosol sample stream in question to be sandwiched between the core stream of carrier gas containing the working fluid vapor and the outer layer formed by the clean air from the inlet 23. It has been found that by using this type of condensing device, the best results can be obtained when the sandwiched gas layer is cylindrically symmetric.

  It is preferable to extend the operating life of the condensing device without the need for frequent filling with working fluid. Significantly extending the operating life between fillings can be achieved by combining the two condensing units with a means for collecting and recirculating the working fluid from the droplets containing particles in the air, passing through the particle detector. is there. Such an assembly can consist of two condensing units and an aerosol flow manipulator with a three-way valve to redirect the flow. The condensing device used in such an assembly is slightly different from the specific embodiment described above, and an example of a suitable condensing device is shown in FIG. In the embodiment of FIG. 11, a gas (for example, air) in which a very small drop containing particles in the air recirculated from the particle counter flows into the inlet 1. In order to prevent the recirculated particles in the air from flowing through the condenser and contaminating the sample gas containing the particles in question, the porous medium is in contact with the evaporation chamber air flow in the evaporation chamber 2. 26 is provided. The porous medium 26 is selected so that it can perform two functions. First, the porous medium must be able to be immersed in the working fluid, so that when heated, it can act as a vapor source and second, it functions as a filter. And must collect microdroplets containing microparticles, thereby preventing vapor contamination in the downstream region of the porous medium 26. In the other embodiments described above, the heating element 3 is located close to the surface of the porous medium 26 and the deposited working fluid is evaporated. However, the thermal contact between the heating element 3 and the porous medium 26 is not important in this embodiment due to the heating effect by the gas flowing into the evaporation chamber 2 via the inlet 1.

  The porous medium 26 is positioned to form a hermetic seal member with the walls of the evaporation chamber 2 so that all gas from the inlet 1 is filtered and all particles in the air are captured. It should be understood from the above. The drops of working fluid collected on the porous support 26 are re-evaporated and released as vapor into the evaporation chamber 2 downstream of the porous medium 26.

  An assembly comprising two condensers of the type described above consumes little or no working fluid and therefore does not need to be filled. Such an assembly is shown in FIG.

  The assembly shown in FIG. 12 comprises two condensing devices 27 and 28, each of which is the condensing device shown in FIG. Three three-way valves 30, 31 and 32 and two on-off valves 33 and 34 direct the fluid flow and allow the working fluid to be recirculated.

  The assembly shown in FIG. 12 functions as follows.

  The air stream containing the nanoparticles in question is flowed to one condensing device (eg, condensing device 28) via a common inlet 35 by appropriately adjusting the three-way valve 30. Microdroplets formed on the nanoparticles in the condensing device are caused to flow to the optical particle counter 29 by the three-way valve 31 while the on-off valve 34 is closed. After being counted, the microdroplet is caused to flow to the other condenser 27 by the three-way valve 32. In the condensing device 27, microdroplets are collected in a porous medium, and the filtered clean air is discharged to the surroundings through the outlet port 35 by opening the on-off valve 33. The evaporation chamber in the condenser 27 remains cold because no voltage is applied to the heating element, so that the working fluid collected in the porous medium is retained.

  After a predetermined period of time, the condenser 27 is heated and the valve position is adjusted so that the condenser 28 can be cooled so that drops of working fluid can be collected. The condensing device 27 that was not previously operating then enters an operating mode where the working fluid previously captured by the porous medium is heated and vaporized into a vapor that is mixed with the gas sample stream as described above. . After passing through the condenser and particle counter, the air stream containing particles and vapor flows to the condenser 28 where the air is filtered and the working fluid is collected as described above with respect to the condenser 27. Thereafter, this cycle is repeated.

  The time required to switch the condenser can be set empirically by trial and error. Normally, it is only necessary to switch the valve after operating for several hundred hours. Thus, this system operates with very little energy and can be easily implemented.

  If necessary, additional special gas filters can be attached to the outlets 35 and 36 to capture the working fluid vapor remaining in the gas stream after filtration with a porous medium. However, the vapor pressure of semi-volatile compounds is so low that using a semi-volatile working fluid such as dimethyl phthalate does not require the use of an additional filter in many applications.

  In each of the embodiments described above, a working fluid sensor, such as a filled glass capillary or dew point sensor (not shown), can be attached to the condensation chamber. For example, a decrease in working fluid can be monitored by a sensor provided in the chamber.

  FIGS. 13 to 16 show other types of condensers used in the condensing apparatus of the present invention. In this embodiment, the condenser has a rectangular cross section.

  By using a condenser having a rectangular cross section, the size of the condenser can be considerably reduced. However, a potential problem due to the rectangular shape of the condenser and in particular the circular inlet and outlet of the condenser is a non-uniform flow rate in the condenser. This causes some of the particles to spend more time in the condenser than others, thus preventing the particles from growing uniformly in the condenser. This makes it impossible to accurately measure the number and size of particles. FIG. 13 to FIG. 16 show a rectangular condenser in which a gas containing vapor flowing through the condenser has a substantially uniform flow rate. In this embodiment, a pair of tubular flow distributors are provided, one attached to one side of a rectangular condenser. One flow distributor is fluidly connected (eg, connected) to the evaporation chamber, and the other flow distributor is fluidly connected (eg, connected) to the particle detector.

  Thus, as shown in FIG. 13, the rectangular flow condenser 103 is provided with the first flow distributor 102 and the second flow distributor 104, which are fluidly connected to the condenser 103. ing. A hot gas (eg, air) saturated with the working fluid flows into the first flow distributor 102 via the inlet 101. The flow distributor 102 is designed to supply a uniform flow to the condenser 103. Accordingly, the end of the first flow distributor 102 facing the inlet 101 is closed (see FIG. 15). A second flow distributor 104 is attached to the outlet of the condenser 103 to reduce flow non-uniformity at the outlet of the condenser 103. The gas stream is discharged from the second flow distributor 104 via the outlet 105.

  FIG. 14 shows the relative positions of the first flow distributor 102, the condenser 103 and the second flow distributor 104.

  FIG. 15 schematically illustrates a flow trajectory within the condenser 103, the first flow distributor 102 and the second flow distributor 104. In this embodiment, the air masses flowing in the tracks 106, 107 and 108 are at approximately the same speed, and therefore remain in the rectangular condenser 103 for approximately the same time, resulting in the formation of droplets of approximately the same size. Is done.

Uniform residence time is achieved by designing the flow distributor so that the internal area of the cross section of the flow distributor is sufficiently larger than the internal area of the cross section of the condenser. As an example, if the cross section of the flow distributor is a circle having an inner diameter Dt, the inner height of the condenser is Hc, and the inner width is Wc, πDt ² > Hc ^* Wc. The ratio of πDt ² / (Hc ^* Wc) is greater than 1.1, preferably greater than 2 and more preferably greater than 3.

  Fluidly connecting the interior of the flow distributors 102 and 104 and the interior of the rectangular condenser by providing the wall of the flow distributor with elongated slots or linearly aligned holes that open into the condenser. Can do. An elongated slot is preferably provided between the flow distributors 102 and 104 and the condenser 103. The longitudinal cross-sectional view of FIG. 16 schematically shows the slots 109 and 110. In this case, the flow uniformity in the condenser is controlled not by the condenser height Hc but by the equation including the slot width Ws (Hc> Ws), so that the inner diameter of the flow distributor can be reduced. it can. The ratio Hc / Wc is greater than 1.1, preferably greater than 2 and more preferably greater than 3.

In another embodiment, the flow distributor has holes evenly distributed along the inlet and outlet of the rectangular condenser 103 instead of two slots. The number of holes Nh is greater than 1, preferably greater than 4 and more preferably greater than 10. The diameter Dh of the hole is sufficiently small and can be obtained from the formula πDt ² > Nh ^* πDh ² . The ratio of πDt ² / (Nh ^* πDh ² ) is greater than 1.1, preferably greater than 2 and more preferably greater than 3.

  In one example of a condenser provided as shown in FIGS. 13-16, the flow distributors 102 and 104 were made of a stainless steel rigid tube having an inner diameter of 7 mm and a length of 40 mm. The condenser 103 was made of a stainless steel rigid sheet with dimensions Wc = 20 mm, Hc = 1.4 mm and Lc = 30 mm. However, the flow distributor can also be made of, for example, PTFE, aluminum, other suitable metals, glass, ceramic or plastic materials.

  The cross-sectional shape of the flow distributor may be rectangular, triangular, elliptical, polygonal, or a combination of simple geometric figures.

  17-19 show the evaporation chamber and associated working fluid reservoir.

  The evaporation chamber (vaporizer) shown in FIG. 17 includes a body 200 that is formed of PTFE and has an internal chamber 216. The evaporation chamber comprises a pair of inlets 220 (not shown in FIG. 17, see FIG. 18) and connection means 202 to a condenser (not shown).

  A heating element is attached to one side surface of the body 200 made of PTFE. The heating element has a mounting portion 206 that is detachably fixed to the wall of the body 200 formed of PTFE, and a rod 210 that extends into the inner chamber 216. The holder 204 holds the attachment portion 206 in a fixed position, and the O-ring is a seal member between the attachment portion 206 and the wall of the body 200. Another O-ring is a seal member between the attachment portion 206 and the rod 210.

  The inside of the rod portion 212 is hollow, and a metal heating wire 222 and a thermocouple 224 are provided (see FIG. 20). The heating wire 222 and the thermocouple 224 are fixed in place by a thermal filler 222, which is a metal filled with solder or epoxy resin, for example.

  Heating wire 222 and thermocouple 224 are connected to a controller (not shown).

  Below the heating element, the body of the evaporation chamber has a recess 214 through which a working fluid such as dimethyl phthalate flows. The recess 214 is connected to a working fluid reservoir 216 via a tube 218 (see FIG. 18).

  As shown in FIG. 20, the rod portion is surrounded by a sleeve 226 of porous material, which in this embodiment is a porous material such as a quartz fiber filter, a glass fiber filter, or a polymer or metal filter. The porous sleeve 226 has a tail 228 that extends into the recess 214 and operates as a shaft that draws working fluid out of the recess 214. The sleeve 226 is held at a predetermined position on the rod portion by a clip 230 provided with a hole through which the working fluid can evaporate and an opening formed on the lower side so as to allow the tail portion 228 of the sleeve 226 to pass therethrough. The recess 228 is surrounded by a shaft holder 231 formed of an inert material such as stainless steel.

  In this embodiment, the heating element is in direct contact with the porous support, thereby reducing the necessary heat applied and evaporating the working fluid to form saturated vapor in the chamber. Takes less time to complete.

EXAMPLES Several examples of the device according to the invention have been assembled and tested and are shown below.

Example 1
In one example configured as shown in FIG. 8, the evaporation chamber (saturation chamber) 2 was formed of stainless steel rigid with a length of 30 mm (with an inner diameter of 12 mm). Stainless steel rigid tubes with an inner diameter of 3 mm were used for the inlet, nozzle and outlet. The cooling element consisted of a small 5V DC fan located 15 mm from the condenser surface. The condenser is formed of a stainless steel rigid tube having an inner diameter of 6 mm and a length of 60 mm, and the heating element is coated with a sufficiently long quartz fiber material so as to be located around the bottom of the stainless steel rigid cylindrical part of the evaporation chamber 2. Consists of heating elements. About 0.5 ml of dimethyl phthalate was injected into the evaporation chamber 2 as a working fluid. Microdroplets formed on the nanoparticles were counted with a MetOne laser optical particle counter. The device was tested against SMPS (TSI), a small SAC dimensional spectrometer (Naneum), and a small 3007 CPC (TSI model 3007). Chromium oxide nanoparticles and atmospheric aerosol were used in the test. In the test, it was found that the apparatus of the present invention can enlarge the nanoparticles to a diameter of 1.2 μm and can set the lower limit of the detection range to 4 nm.

Example 2
The aerosol particle number density (N) measured using the apparatus shown in FIG. 2 connected to a MetOne laser optical particle counter, and the aerosol particle number density (N) measured using a small 3007 CPC manufactured by TSI. A comparison was made. The clean air flow flowing into the evaporation chamber 2 via the inlet 1 was set at 0.3 liter / min, and the sample gas flow flowing through the inlet 8 was set at 0.5 liter / min. Chromium oxide nanoparticles and atmospheric aerosol were used in the comparative test.

  The results are shown in FIG. 9, where the data points of the device of the present invention are indicated by black squares and the data points of 3007 CPC manufactured by TSI are indicated by white diamonds. In FIG. 9, D is an average diameter (nm) when measured by a standard method.

  It was found that the diameter of the nanoparticles can be expanded to 1.2 μm by the apparatus of the present invention. The lower limit of detection of the device of the present invention was 3 nm. As is clear from FIG. 9, the detection lower limit of the apparatus of the present invention is lower than the detection lower limit of CPC3007 (manufactured by TSI).

Equivalents It will be readily apparent that various changes and substitutions to the specific embodiments of the invention described above can be made without departing from the principles of the invention. All such modifications and alternatives are intended to be included in this application.

Claims (9)

In a condenser configured to be used in an apparatus that increases the size of gas entrained particles and allows the gas entrained particles to be detected by a particle detector;
The condenser is in fluid communication with the outlet of the evaporation chamber of the device in use;
The condenser has an outlet for connection to the particle detector;
The condenser is provided with means for removing condensed material from the inner wall of the condenser,
The means for removing the condensate has one or more exhaust ducts extending over its entire length or part thereof, the exhaust duct being connected to the condenser by a permeable wall or membrane through which liquid condensate can pass. A condenser having one or more outlets that are separated from the interior of the pump and connectable to a pump for extracting liquid condensate from the discharge duct.   The condenser according to claim 1, wherein the discharge duct is disposed within the condenser over at least a portion of the length of the condenser by one or more longitudinally permeable walls or membranes. It is formed by dividing | segmenting a condenser.   The condenser according to claim 2, wherein the permeable wall or the membrane is provided with a capillary that allows condensate to flow from the inside of the condenser to the discharge duct.   4. The condenser according to claim 3, wherein the wall or membrane is formed from (a) a ceramic or stainless steel filter material having a capillary size less than 0.1 mm, or (b) a porous material. Features a condenser.   The condenser according to any one of claims 1 to 4, wherein to control the lower limit of the detection size of the problematic particles detectable by the particle detector, thereby obtaining the size distribution of the nanoparticles, A condenser comprising means for changing the temperature of the condenser or a part thereof. The condenser according to any one of claims 1 to 5,
A condenser body comprising an inlet, an outlet, and a hollow interior having an inner length, an inner width and an inner height;
An inflow flow distribution pipe connected to the inlet of the condenser body and extending across the inner width of the condenser body;
An outlet flow distribution pipe connected to the outlet of the condenser body and extending across the inner width of the condenser body;
The inner height of the condenser body portion is lower than the corresponding inner height of each of the inflow flow distribution pipe and the outflow flow distribution pipe,
Each wall of the inflow flow distribution pipe and the outflow flow distribution pipe is provided with one or more slots or holes communicating with the hollow interior of the body portion of the condenser. A condenser having a flow path leading to the outflow flow distribution pipe through a hollow interior of the vessel.   The condenser according to claim 6, wherein an inner cross-sectional area of each flow distribution pipe is larger than an inner cross-sectional area (inner width × inner height) of a body of the condenser.   8. The condenser according to claim 7, wherein the ratio of the inner cross-sectional area of each flow distribution pipe to the inner cross-sectional area (inner width x inner height) of the condenser body is 1.1, 2, or 3 A condenser characterized by its large size. 9. A condenser according to any one of claims 6 to 8, wherein the wall of the flow distribution pipe has an elongated slot that opens into a hollow interior of the condenser body, the inner height of the condenser body. The ratio of the width to the width of the slot is greater than 1.1, 2 or 3.

Images